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7 Apr 2010 Paul Dauncey 1
Tech Board: DECAL beam test at DESY, March 2010
Paul Dauncey
7 Apr 2010 Paul Dauncey 2
Main aims (Tech Board 3 Feb)• SPiDeR had to be more generic than just ILC
• Certainly more than just ILC DECAL
• DECAL sensor (TPAC) not the only sensor being tested
• Fortis and Cherwell sensors for studying tracking applications
• Two main strands
• DECAL performance
• General performance of CMOS MAPS
• For DECAL
• Realistic resolution depends on charged particle density in EM shower core
• Predicted by simulation to be O(100/mm2) but not verified at 50m granularity
• Main aim this year is to measure real shower density with electrons
7 Apr 2010 Paul Dauncey 3
MAPS variants (Tech Board 3 Feb)
• Deep P-well vs non-deep P-well
• Expect deep P-well to have higher collection efficiency
• High-resistivity vs standard silicon
• Collection by diffusion, so slow; O(100ns)
• With high-resistivity, can have electric field to suck out charge; faster, more efficient and probably more radiation hard
• Epitaxial layer depth; 5 vs 12 vs 18m
• Changes amount of signal charge generated
7 Apr 2010 Paul Dauncey 4
DESY beam test (Tech Board 3 Feb)• Three weeks as main user, limited to 1-6GeV electrons
• Most of March; overlaps UTA collaboration meeting and LCWS10
• Technically, close to a repeat of CERN beam test so “straightforward”
• Use EUDET telescope; DAQ integration ongoing
• Measure efficiency of all sensors variants available for “MIPs”
• Compare with CERN results with pions to check for non-MIP effects
• Measure shower core densities in EM showers
• As a function of energy and of tungsten converter depth
• Need accurate tracking to locate shower centre
7 Apr 2010 Paul Dauncey 5
SPiDeR shifters• University of Birmingham
• H. Bansil, T. McLaughlan, T. Price, N.Watson
• University of Bristol
• D. Cussans, J. Goldstein, R. Page, J. Velthuis
• University of Edinburgh
• H. Tabassam
• Imperial College London
• P. Dauncey
• University of Oxford
• R. Gao
• Rutherford Laboratory
• M. Stanitzki, J. Strube, G. Zhang
• Total: 14 people for three weeks = 54 shifts (72 person-shifts)
7 Apr 2010 Paul Dauncey 6
Complete TPAC system
DAQ PC
USB_DAQ master Sensor mechanical support
CAEN power supply USB_DAQ readout
7 Apr 2010 Paul Dauncey 7
Data-taking overview
• 47M bunch trains × 3.2ms/bunch train = 150k sec live time = 42 hours
• Corresponds to 8% duty cycle overall
• Mainly due to DAQ rate; 40Hz bunch train rate gives 13% duty cycle
• Roughly 65% running, averaged over whole three weeks
Accelerator maintenance period
7 Apr 2010 Paul Dauncey 8
Temperature• Temperature was significant issue at CERN last summer
• High temperatures ~40C meant sensors could lose their configuration
• Always below 30C at DESY
• Much more stable operation
• Jumps due to changes of mode of operation, i.e. layout of sensors in stack
Hi-tech () air blower
7 Apr 2010 Paul Dauncey 9
EUDET telescope• Not as useful as we had hoped for DECAL work
• Had not been run continuously since being installed at DESY
• Operation was rather variable for the first two weeks
• Heroic efforts from Ingrid and (particularly) Igor Rubinsky helped to fix it
• DECAL stack could not get closer than ~1m from the last telescope plane
• Low momentum beam so completely multiple scattering limited
• Resolution at DECAL sensors ~200-500m » sensor pixel size
7 Apr 2010 Paul Dauncey 10
Tracking mode
• Four standard sensors in outer layers
• Construct tracks using these only; no need for EUDET telescope
• Two sensors-under-test in the inner two layers
• Project track to these to measure efficiency
• Identical method (and analysis) to CERN
7 Apr 2010 Paul Dauncey 11
Tracking mode II• Used adapted version of George’s semi-online monitoring
• E.g. number of sensor pixels firing vs pixel time difference from PMT hits
• All standard sensors • One non-deep p-well sensor
7 Apr 2010 Paul Dauncey 12
Tracking mode III
Hi-res
Standard
CERN
Type Number tested
Standard 4
Non-deep p-well 2
12m hi-res 3
18m hi-res 2
• Only fully tested two of the four variants at CERN
• Did all four with at least two sensors each at DESY
• Threshold scan for all cases
7 Apr 2010 Paul Dauncey 13
Shower mode
• Inserted differing numbers of tungsten sheets between sensors
• Each sheet was 3mm, corresponding to 3/3.5mm = 0.86X0
• Fallback due to uncertainty of EUDET telescope operation
• Use four TPAC sensors for pre-tungsten tracking
7 Apr 2010 Paul Dauncey 14
Shower mode II
• Sensor hit correlations for layer 3 (before tungsten) and layer 4 (after tungsten)
• Both vs hits in layer 0
7 Apr 2010 Paul Dauncey 15
Shower mode III• Also did copper (and a very small amount of iron and lead)
• Radiation length of copper =14.3mm (c.f. tungsten = 3.5mm)
• Limited for copper in number of X0 which would fit into stack
Material Tungsten Copper
0.44X0
0.9X0
1.7X0
3.4X0
5.1X0
6.9X0
8.6X0
10.3X0 • All done at 1, 2, 3, 4 and 5 GeV
• No 6 GeV beam as DESY2 only running at 6.3GeV
7 Apr 2010 Paul Dauncey 16
CERN beam test, May/Sep 2010• Requested two weeks as main user, 10-100GeV electrons, 120GeV pions
• Also requested EUDET telescope so identical DAQ to DESY
• Now know it is not essential for TPAC (but is for other SPiDeR tests)
• Extend shower density measurements up to 100GeV
• Much bigger level arm; 1-100GeV rather than 1-5GeV
• Better check of simulation
• New idea: if EUDET telescope performing well
• Cross-check density measurements using telescope stand-alone
• Place tungsten between the two arms and measure hits in downstream arm
• Cross-check any MIP efficiencies if any variants look odd
• Using pions (in parallel with other SPiDeR tests)
• But still very limited effort available
• Probably can just about cover shifts
• Main problem would be analysis, particularly towards the end of 2010
• Have a meeting in two weeks to decide if we will go ahead with beam runs